Styrene resins represented by ABS resin are widely used for the production of automobiles, household electrical appliances, OA equipments or the like due to its superior moldability, mechanical properties, chemical resistance and secondary processability.
However, when parts of styrene resins represented by ABS resin come into contact with and rub against another part made of other resins such as polyethylene and polyvinyl chloride or another part such as a lining sheet or a foam made of chloroprene rubber, natural rubber, polyester or polyethylene, squeaking noises (rubbing noises) may be generated. For example, in a ventilator made of ABS resin is installed a valve shutter using a chloroprene rubber foam or the like as a sealing material in order to adjust an air quantity. If the valve shutter is rotated for air quantity adjustment, a case of the ventilator rubs against the sealing material, so that squeaking noises may be generated.
Moreover, it is known that when parts made of styrene resins rub against each other, squeaking noises tend to be generated. Therefore, it is avoided to use parts made of styrene resins in combination in places where the parts come into contact with and rub against each other, for example, by vibration, rotation or the like.
Since the styrene resins such as ABS resin and ASA resin are amorphous resins, they are higher in coefficient of friction as compared with crystalline resins such as polyethylene, polypropylene and polyacetal, and it is well known that, like an air outlet of an air conditioner in an automobile or buttons of a car audio system, when fitting with a member made of another resin, a stick slip phenomenon as illustrated in FIG. 1 occurs to generate unpleasant sounds (squeaking noises) because of a large coefficient of friction. The stick slip phenomenon is a phenomenon that is generated when two objects rub against each other. As illustrated by a model of FIG. 2(a), when an object M connected with a spring is placed on a driving table that moves at a driving speed V, the object M moves toward the right direction first as illustrated in FIG. 2(b) together with the table moving at the driving speed V by the action of a static frictional force. When the force by which the object M is to be restored to its original position becomes equal to the static frictional force, the object M starts to slip in the opposite direction to the driving speed V. At this time, the object M comes to receive a kinematic frictional force, and the slip is stopped when the force of the spring becomes equal to the kinematic frictional force as illustrated in FIG. 2(c), so that the object M comes again into a state where it attaches on the driving table and it moves again in the same direction as the driving speed V (FIG. 2(d)). This is called a stick slip phenomenon. As illustrated in FIG. 1, it has been said that if the difference Δμ between the coefficient of static friction μs of the upper end of a saw wavy form and the coefficient of friction μ1 of the lower end of a saw wavy form is large, squeaking noises tend to be generated easily. A dynamic friction coefficient is a middle value between μs and μl.
When those are used as automobile interior parts and the like, such a squeaking noise is a major cause that spoils comfortableness and silence when riding a car, and therefore reduction of squeaking noises is demanded strongly.
On the other hand, it is known that the stick slip phenomenon occurs remarkably when the friction velocity dependency of a coefficient of friction determined on the basis of the Amonton-Coulomb's law takes a negative value (see non-patent document 1), and it is possible to inhibit the occurrence of the stick slip phenomenon and reduce the generation of squeaking noises by bringing the friction velocity dependency of the coefficient of friction close to zero or to a positive value greater than zero.
In order to prevent such squeaking noises, a method of applying Teflon (registered trademark) coating to the surface of a member, a method of mounting a Teflon (registered trademark) tape, a method of applying a silicone oil, etc. have been performed. However, the step of mounting or applying is very complicated and requires time and effort, and there is a problem that the effect does not continue when being placed under high temperatures for a long time.
As a method for changing the properties of the material itself, a method of incorporating a silicone oil into an ABS resin and a method of incorporating an epoxy-containing olefin copolymer into an ABS resin have been proposed. For example, there have been disclosed a technology of incorporating an organosilicon compound into a resin composed of a polycarbonate resin and an ABS resin (see patent document 1), a technology of incorporating a flame retardant, a flame retarding aid and a silicone oil into an ABS resin (see patent document 2), a technology of incorporating a silicone oil into a rubber-modified polystyrene resin (see patent document 3), a technology of incorporating an alkali (earth) metal salt of an alkane sulfonate surfactant into an ABS resin (see patent document 4), and a technology of incorporating a modified polyorganosiloxane having at least one reactive group selected from among an epoxy group, a carboxyl group and an acid anhydride group into an ABS resin (see patent document 5).
However, an effect of reducing squeaking noises obtained by these methods is not sufficient. Even if the effect of preventing squeaking noises is considerably exhibited just after molding, the durability of the effect is poor, and in particular, there is a problem that the effect deteriorates remarkably when being placed under high temperatures for a long time.
Moreover, when the parts made of styrene resins represented by ABS resins are assembled in combination, even with those technologies, the sufficient effect of reducing squeaking noises cannot be obtained and thus there was a problem that the range of usage was limited.